I'm fairly new to magic, and I'm trying to understand rulings.
How does the interaction between Kess, Dissident Mage and Splinter Twin work? I have enchanted Kess, Dissident Mage with Splinter Twin. Can you you tap Kess for the token and then use the tokens ability before having to graveyard it due to the legend rule?
If the token can use Kess' ability can you use both Kess to play the same card from the graveyard?
The legend rule is a state based action. Those are checked right after a spell or ability has finished resolving, before any player gets priority. Since you need priority to cast a spell via Kess, you lose the original or the token before you can cast a spell via Kess or its copy. So no, you cannt do this.
However, in case that you have two or more Kesses out (Mirror Gallery, Helm of the Host, Sakashima the Impostor, Spark Double, etc.) you still can cast a spell from the graveyard only once. Because casting a spell includes (as the very first step) to move the card from where it is (here the graveyard) to the stack. Since the card is no longer in the graveyard after you finished the casting process and have priority again, it is not available for the other Kesses to cast with.
No, to both of your questions. For the first, creating a token copy of Kess, Dissident Mage will cause the legendary rule to make you send one of them to the graveyard. This is a state-based action, which means it happens instantaneously upon a player receiving priority and can not be responded to. As the token's ability requires you to have priority to cast the spell, you will never be able to use its ability unless you have something like Mirror Gallery or have the copy be non-legendary via something like Helm of the Host or Spark Double.
As for your second question, Kess's ability exiles the spells she casts when they try to go to the graveyard, so you won't be able to play the same card twice with her ability unless you have something like Pull from Eternity.
How does the interaction between Kess, Dissident Mage and Splinter Twin work? I have enchanted Kess, Dissident Mage with Splinter Twin. Can you you tap Kess for the token and then use the tokens ability before having to graveyard it due to the legend rule?
If the token can use Kess' ability can you use both Kess to play the same card from the graveyard?
Splinter Twin
Kess, Dissident Mage
The legend rule is a state based action. Those are checked right after a spell or ability has finished resolving, before any player gets priority. Since you need priority to cast a spell via Kess, you lose the original or the token before you can cast a spell via Kess or its copy. So no, you cannt do this.
However, in case that you have two or more Kesses out (Mirror Gallery, Helm of the Host, Sakashima the Impostor, Spark Double, etc.) you still can cast a spell from the graveyard only once. Because casting a spell includes (as the very first step) to move the card from where it is (here the graveyard) to the stack. Since the card is no longer in the graveyard after you finished the casting process and have priority again, it is not available for the other Kesses to cast with.
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As for your second question, Kess's ability exiles the spells she casts when they try to go to the graveyard, so you won't be able to play the same card twice with her ability unless you have something like Pull from Eternity.
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